A key feature of autism is the difficulty people with the disorder have in engaging socially with others. Over the past decade Dr. Porges has studied a neurobiological model of the social engagement system that he calls the polyvagal theory. The theory is based on ideas about how the autonomic nervous system, which controls bodily functions such as breathing, heart rate, stress responses and emotional responses, evolved in humans and other mammals. Dr. Porges argues that the nerves that regulate the body's physiological state—heart rate, stress hormones, immune function—are linked to the nerves that regulate eye gaze, facial expression and listening. These skills are a critical part of the social engagement system. For some people—people with autism, for example—their nervous system misreads the environment and turns on the defenses, making social interaction difficult or impossible. This grant will provide bridge funding so the researchers can continue their research program of testing the polyvagal theory by recruiting participants for new studies that will use more refined measures of social engagement. The funding will also allow them to complete data collection, data analysis and publication of work that's already under way. What this means for people with autism: This research takes a unique perspective of social engagement behavior, providing a clear, testable theory of a neurological system that controls it. Results from this groundbreaking work may lead to the development of new laboratory-based measures of social engagement behavior that clinicians and researchers can use to assess individuals with autism.